Known in the art and technology are multi-step transmission with two counter shafts and a central main shaft. The gearwheels, which are mounted loosely on the rotating main shaft, follow the same rotation direction and only engage the main shaft when the particular gear is needed to deliver and to transmit the torque. Therefore, the gear wheels are also called idle gears.
Idle gears are connected to the floating main shaft, having a certain amount of play regarding the radial direction. Hereby, load compensation of the energy flow is achieved between the two lay-shafts. The idle gears, which mesh with the counter shaft wheel's gearing are guided in the radial direction by the counter shaft gears, i.e., each idle gear mounted on the main shaft and having a radial play, will center itself under the gearing force of the counter shaft gear wheels. That condition occurs when the corresponding shift step is selected, the clutch being engaged, and the motor works in the push or the pull position. Thus, an optimum in regard to load compensation during the torque transfer can be achieved. The idle gears, currently not being assigned to any gear shift steps, are idling in a load free condition. In that load free condition, the idle gears are floating within the gearing's play, meaning that they possess, in relationship to the main shaft, the leeway of moving within a radial direction and a circumferential direction.
Because of the idle gear's versatile bearing, an unpleasant rattling noise occurs during operation, due to the fact that the gears, which are part of the no-load gear shift condition, experience accelerations in the circumferential and radial directions, caused by tolerances in manufacturing and by rotation oscillation during a push or pull condition when activating or deactivating the power train. Due to the mentioned acceleration and their motion, the idle gears strike the components and parts right next to them. As an example, one gear's flank strikes the flank of the gear which it is supposed to work with, due to tolerances and play, a main reason why the rattling noise of gears under the no-load shift position is being generated. During the shift position in reverse, additional noise, on top of the lay-shaft gears and idle gears, is being generated through the intermediate gears.
Suggestions and proposals have already been presented to reduce the rattling noise in multi-step transmissions with two counter shafts. As an example and representation of the art, DE 102004057126 A1, presents an arrangement to reduce the idle gear's axial movement in a transmission having two counter shafts, whereby the main shaft's engagement device presses at least one of the idle gears against a run-up disk. Thereby, but not limited to it, the unwanted rattling noise can be avoided. The described engagement device requires an additional effort during the manufacturing of the transmission, and is exposed during operation to friction between the engagement device and idle gear, resulting in additional wear.